JOIN USResearchers at the University of Missouri (MU) and Ohio University found that the thick layers of cartilage in some dinosaurs' joints that didn't fossilise might have added more than one foot to their heights.
According to them, the ends of many dinosaurs' long bones, including leg bones such as the femur or tibia, are rounded and rough and lack major bony joint structures.
This indicated that very thick layers of cartilage probably helped form the joints connecting these bones, said researcher Casey Holliday, an evolutionary anatomist at the University of Missouri.
"And this would have added significant height to certain dinosaurs," Holliday was quoted as saying by LiveScience.In contrast, mammals have bony joint structures and much less of the soft-tissue cartilage, he said.
The scientists reached these conclusions by examining ostriches and alligators -- the closest, modern-day relatives of the extinct giants.
For their research, they made casts of their bones with cartilage and then removed the cartilage and compared the bones with the casts.They found the lengths of alligators' and ostriches' limbs included between six per cent and 10 per cent cartilage.
They next studied the fossilised limbs of different dinosaurs, including famous carnivorous theropods such as T. rex and Allosaurus as well as giant herbivorous sauropods and ornithischians such as Brachiosaurus and Triceratops, respectively.
From the evidence, the researchers concluded that certain dinosaurs possessed a significant amount of cartilage in their joints.
Although their analysis, published in the journal PLoS ONE, suggested many theropods were only modestly taller, ornthischians and sauropods might have been 10-per cent taller or more. For example, Brachiosaurus, once thought to be 42 feet tall, may actually have been more than one foot, or 12.8 cm, taller.
"This may seem trivial -- however, this is a large amount of cartilage," Holliday said.
The extra cartilage may have helped the giant herbivores absorb the increased amount of stress resulting from their enormous sizes, he conjectured, "but we're still not really sure".
Holliday added that birds, the closest living relatives of the extinct theropods they studied, also have less cartilage in their joints, and that "less cartilage might be a sign of a more active lifestyle, higher metabolic rate and faster growth rate that we see in theropods and birds."
Holliday said that their findings could help shed light on dinosaur movements and posture. "We could use what we know about cartilage to make 3-D models of their joints to try and test how they were able to move."
"Bones can't always speak for themselves," added researcher Lawrence Witmer, an anatomist at Ohio University.
"To understand how dinosaurs moved, we need to analyse the bones as they were inside their bodies, including their cartilage."